Method for carrying out infrared data transmission

ABSTRACT

A method is described for infrared data transmission between several transmitter units (S 1  to S 4 ) and a common receiver station ( 2 ), with the individual transmitter units (S 1  to S 4 ) transmitting the data to be transmitted in a blockwise manner to the receiver station ( 2 ) in a time interval with respect to each other. In order to provide advantageous preconditions for the method it is proposed that the respective data blocks (d 1  to d 4 ) to be transmitted are transmitted repeatedly in a transmission interval (T) of the same length for all transmitter units (S 1  to S 4 ) according to the maximum number of transmitter units (S 1  to S 4 ), with the length of the repetition intervals (i 1  to i 4 ) which differ for all transmitter units (S 1  to S 4 ) differing at least by twice the transmission time for a maximum data block size, and that the shortest repetition interval (i 1 ) corresponds at least to the multiple of the double transmission time for a maximum data block size, which multiple corresponds to the maximum number of transmitter units (S 1  to S 4 ).

FIELD OF THE INVENTION

The invention relates to a method for infrared data transmission betweenseveral transmitter units and a common receiver station, with theindividual transmitter units transmitting the data to be transmitted ina blockwise manner to the receiver station in a time interval withrespect to each other.

DESCRIPTION OF THE PRIOR ART

In order to control a base station such as a computer, audio or videosystems, gaming consoles or the like through several control devices viainfrared data transmission, it needs to be ensured that the datatransmitted by the individual control devices, which data is transmittedin a blockwise manner, can be received by the base station in a mannerso as to be unimpaired by the data transmission of other controldevices. For this reason, different carrier frequencies are assigned inknown infrared transmission methods to the different transmitter unitsof the control devices or the data blocks are transmitted by thetransmitter units in time intervals successively, which each require acertain amount of effort. While in the use of different carrierfrequencies it is not only necessary to have different transmitter unitsbut also to have receiver units adjusted to the respective carrierfrequencies, the time-staggered transmission of the data combined intodata blocks requires a respective control of the transmitter units ofthe control devices from the receiver station, which on the part of thereceiver station necessitates a respective transmitter unit and on thepart of the transmitter units additional receiver units for the mutualtime coordination of the control devices, although in many applicationsdata merely need to be sent from the control devices to the basestation.

In order to ensure a secure reception of the data sent by severalcontrol devices to a common base station without having to assign to thecontrol devices any separate carrier frequencies or to synchronize thetransmitter units of the control devices, it is finally known (DE 36 24507 A1) to transmit the data to be transmitted repeatedly inpredetermined time intervals which are chosen separately for eachcontrol device. Although this ensures the complete reception of the datafor each control device, the control devices are placed at aconsiderable disadvantage with respective longer time intervals betweenthe data output. For this reason it was proposed to choose thetransmission pauses between the transmission pulses differently for eachtransmitter unit, so that for each transmitter unit a different patternof different transmission pauses is obtained. This increases theconstructional complexity for the transmitter units however. Moreover,blockwise data transmission is not possible.

SUMMARY OF THE INVENTION

The invention is thus based on the object of providing a method forinfrared data transmission between several transmitter units and acommon receiver station of the kind mentioned above in such a way that asecure data transmission is enabled with a low amount of effort withouthaving to use different carrier frequencies or having to trigger thetransmitter units from the common receiver station.

This object is achieved by the invention in such a way that therespective data blocks to be transmitted are transmitted repeatedly in atransmission interval of the same length for all transmitter unitsaccording to the maximum number of transmitter units, with the length ofthe repetition intervals which differ for all transmitter unitsdiffering at least by twice the transmission time for a maximum datablock size, and that the shortest repetition interval corresponds atleast to the multiple of the double transmission time for a maximum datablock size, which multiple corresponds to the maximum number oftransmitter units.

Since as a result of this measure the data combined into data blocksneed to be transmitted several times within a predetermined transmissioninterval (namely in a number corresponding to the maximum number oftransmitter units), it is necessary (under the precondition that therepetition intervals of the individual transmitter units differ by apredetermined minimum amount in their length), that each data blocktransmitted by a transmitter unit must be received at least once in itsfull length by the receiver station, without being influenced by datatransmissions of the other transmitter units. Since as a result of apredetermined maximum data block length a time offset of two data blockstransmitted by different transmitter units up to the amount of thetransmission time for one data block leads to an overlapping receptionof the two data blocks in the receiver station, the minimum distancebetween repetition intervals of the individual transmitter units mustcorrespond to the double transmission time for a maximum data blocksize. Moreover, the shortest repetition interval must not be shorterthan the multiple of the double transmission time for a maximum datablock size (which multiple corresponds to the maximum number oftransmitter units), because otherwise the data blocks of all transmitterunits cannot be transmitted with the required safety intervals accordingto the data block length without mutual overlapping within the shortestrepetition interval. This however is a precondition for an at leastsingle overlap-free transmission of each data block, irrespective of therespective transmission time of the transmitter units. If the datablocks each contain in the usual manner an identifier for thetransmitter unit from where they were sent, a secure unilateral datatransmission from the transmitter units to the receiver station isenabled in a simple manner that is independent of the respectivetransmission time of the transmitter units. It is necessary to observethe predetermined transmission interval between the transmission ofdifferent data blocks of a transmitter unit however.

In order to enable the control of transmitter units for infrared datatransmission to a common receiver station according to the invention,the data which are to be transmitted, combined in a data block and savedto a memory of each transmitter unit, must be repeatedly read out to thetransmitter unit via a control unit for transmission to the receiverstation. The repetition interval is predetermined by the programdepending on the number of transmitter units and the data block length,which is different for each transmitter unit because these repetitionintervals must have a time grading depending on the data block length.As a result of the time elements assigned to the individual transmitterunits, the repetition intervals of the individual transmitter unitswhich are adjusted to each other with respect to their length can bepredetermined without any further problems. The data to be transmittedcan be read into the memory in a conventional manner by means of areader device which can be configured in many different ways and canconsist of a keyboard, mouse or a control lever.

BRIEF DESCRIPTION OF THE DRAWINGS

The method in accordance with the invention is now explained in closerdetail by reference to the drawings, wherein:

FIG. 1 shows a device in accordance with the invention for infrared datatransmission between several transmitter units and a common receiverstation in a simplified block diagram;

FIG. 2 shows an infrared carrier beam which is modulated according to adata block to be transmitted;

FIG. 3 shows a possible transmission protocol for four transmitter unitscooperating with a common base station, and

FIG. 4 shows the infrared signal received by the receiver stationaccording to the transmission protocol according to FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the embodiment of FIG. 1 which shows merely one of severalreceiver units 1, the data to be transmitted from the individualtransmitter units 1 to a common receiver station 2 are read via an inputdevice 3 into a memory 4, which occurs by means of a control unit 5which on its part is connected on the one hand to a program memory 6 andon the other hand to a timing element 7. This control unit 5 is used forcombining the stored data into a data block depending on therespectively predetermined program and forwarded to a transmitter module8 for transmission to the receiver station 2. An infrared carrier ismodulated in this transmitter module 8 according to the data block to betransmitted, as is indicated in FIG. 2 for example. FIG. 2 shows that bymodulating the carrier frequency of 56 kHz for example a sequence of 8bits with a period of 500 μs is obtained. Each bit is composed of apulse sequence and pulse break of 250 μs each, so that a bit of a pulsesequence with a subsequent pause can be assigned a logical “1” and a bitwith a pause preceding the pulse sequence can be assigned a logical “0”.The individual bits of the bit sequence shown in FIG. 2 are associatedwith certain information to be transmitted. As a result, the first bitin the bit sequence forms a start command for example for the receiverunit 2, whereas the next two subsequent bits contain the identifier forthe individual transmitter units 1, which requires two bits for fourtransmitter units 1. Since the data block according to FIG. 2 istransmitted not only once but several times (which occurs four times inthe case of four transmitter units 1), the subsequent two bits canrepresent the actual repetition number, whereas the last three bitscontain the actual information to be transmitted, as were enteredthrough the input device 3. These last three bits can represent the codeof a pressed button.

FIG. 3 shows the time-related send protocol of four transmitter units 1under the unfavorable assumption for the transmission that alltransmitter units S1 to S4 are started simultaneously, so that the datablocks transmitted within a send interval T by the individualtransmitter units S1 to S4 arrive simultaneously in the receiver station2, leading to a signal F according to FIG. 4 which can no longer beevaluated. The data blocks d1 to d4 are not transmitted only once, butaccording to the number of the transmitter units (i.e. four times). Therepetition intervals i1 to i4 differ in their length, namely at least bytwice the transmission time of the data blocks d, to d4. The smallestrepetition interval i1 corresponds at least to four times the doubledata block length, as is shown in FIG. 3. Under these preconditions itis ensured irrespective of the respective start time of the individualtransmitter units S1 to S4 that in the predetermined transmissioninterval T each data block d1 to d4 is transmitted at least oncecompletely to the receiver station 2 and without impairment by datablocks of other transmitter units. Under the assumption of FIG. 3, onlytwo erroneous transmissions will occur in connection with thetransmitted data blocks d1 to d4, as are designated in FIG. 4 withreference F.

The data blocks d1 to d4 as transmitted by the individual transmitterunits 1 in the described manner are received in the receiver station 2via a receiver stage 9 which is common to all transmitter units 1 andare supplied to an evaluation circuit 10 which is connected to arespective program memory 11 in order to allocate the arriving datablocks and to enable the deciphering of the same. This evaluationcircuit 10 is connected in the usual manner again with a data memory 12and a timing element 13 in order to secure a respective data processing.The received data can then be forwarded through an output device 14 forcontrolling the connected base station.

1. A method for infrared data transmission between several transmitterunits and a common receiver station, with the individual transmitterunits transmitting the data to be transmitted in a blockwise manner tothe receiver station in a time interval with respect to each other,wherein the respective data blocks to be transmitted are transmittedrepeatedly in a transmission interval of the same length for alltransmitter units according to the maximum number of transmitter units,with the length of the repetition intervals which differ for alltransmitter units differing at least by twice the transmission time fora maximum data block size, and that the shortest repetition intervalcorresponds at least to the multiple of the double transmission time fora maximum data block size, which multiple corresponds to the maximumnumber of transmitter units.
 2. A device for infrared data transmissionbetween several transmitter units and a common receiver stationaccording to claim 1, with the transmitter units being associated on theone hand with memories for the data combined in a data block to betransmitted and on the other hand with a control unit connected totiming elements for reading out the transmitted data blocks from thememories, wherein memories (4) for the transmitted data blocks (d) canbe read out repeatedly within a send interval (T) predetermined withrespect to its duration depending on the number of the transmitter units(1) in repetition intervals (i1 to i4) differing for each transmitterunit (1), which intervals extend step by step from a minimum interval(i1) depending on the number of the transmitter units (1) and the doubletransmission time for a data block by at least the double transmissiontime for a data block.